cannot start mongrel after Snow Leopard upgrade : Wrong Architecture !!!

(MacBook Core 2 Duo.. but 32-bits kernel... upgraded to SL)
Rails 2.3.4 / Ruby 1.8.7
fine with Webrick
Booting WEBrick
=> Rails 2.3.4 application starting on http://0.0.0.0:3000

but trying to start Mongrel ( btw should be the default in dev mode
when installed ?)

mongrel_rails start -d

/usr/local/lib/ruby/gems/1.8/gems/mongrel-1.1.5/bin/../lib/
http11.bundle: dlopen(/usr/local/lib/ruby/gems/1.8/gems/mongrel-1.1.5/
bin/../lib/http11.bundle, 9): no suitable image found. Did find:
(LoadError)
  /usr/local/lib/ruby/gems/1.8/gems/mongrel-1.1.5/bin/../lib/
http11.bundle: mach-o, but wrong architecture - /usr/local/lib/ruby/
gems/1.8/gems/mongrel-1.1.5/bin/../lib/http11.bundle

another example of the big mess in Rails dev env. w Apple SL !! is my
architecture i386 ? or x86-64 .... ? as I cannot boot the 64-bit
kernel on my MacBook....

what should I modify ??

thanks for any info

uninstall/install your architecture specific gems.

Doing something like sudo gem update --system; sudo gem pristine --all

done .. re-installed ( ruby 1.9.and 1.8.7, rails 2.3.4 and all gems)
but I had to care about error in both make ruby........ need to
install readline 6.0 in usr/local to avoid errors...

thanks